Complex carbohydrates or glycans are involved in almost every physiological or pathological process. Advances in understanding the biological roles played by glycans, along with the factors that influence or alter their functions will provid important avenues for the development of new therapeutics, and diagnostics. In recognition of opportunities to advance the impact of glycoscience on human health, we have assembled a team of five senior investigators that will work cooperatively on three related research projects to exploit unique capabilities of a Core to produce recombinant mammalian glycosyltransferases. The research projects will 1) study biochemical and structural aspects of glycosyltransferase to define their acceptor specificities at a molecular and structural level 2) exploit the enzymes in a novel chemoenzymatic approach to provide glycans for structure activity relationship studies, aid in the development of the next generation of glycan microarray and as analytical standards; 3) develop sugar nucleotide donors modified by a chemical reporters to label subsets of glycoconjugates for visualization, capture and identification of glycans in cellular models of disease. The three projects have high synergy. Each requires a relatively large panel of glycosyltransferases that will be produced by a core. In addition, they will generate reciprocal knowledge and resources. Project 1 and 3 will perform complementary studies to uncover glycosyl acceptor specificities of glycosyltransferases. Information about glycosyl acceptor specificities of glycosyltransferases will be employed by Project 2 to prepare glycans that otherwise are not accessible by chemo-enzymatic synthesis. Project 2 will generate synthetic glycans that will be employed by Project 1 for in depth studies of glycosyl acceptor specificities. Structural studies by Project 1 will provide important information for project to design of sugar nucleotide donors modified with a chemical reporter for cellular studies in the context of human disease.